1. Field of the Invention:
This invention relates to an air suspension for a vehicle provided with an air spring, and more particularly to an air suspension capable of varying the spring constant.
2. Description of the Prior Art:
An air suspension capable of varying the spring constant can be varied the spring constant by controlling communication between a main air chamber and an auxiliary air chamber provided in association with a shock absorber including a cylinder, a piston and a piston rod.
A valve unit for controlling the communication between both air chambers is generally provided in association with an elastic assembly for supporting elastically the piston rod on a car body. That is, a valve container permitting the penetration of an end of the piston rod and receiving a valve body is disposed in said elastic assembly and is fixedly attached to an inner tube of said elastic assembly. Said valve body is provided with a path communicating to the main air chamber, and said valve container is formed with at least a larger diameter path and a smaller diameter path capable of communicating to said path of the valve body. Also, air paths communicating to the auxiliary air chamber through said elastic assembly consisting of the inner tube, a tubular elastic member and an outer tube are provided respectively corresponding to the larger and smaller diameter paths of said valve container.
In said air suspension can be interrupted the communication between both air chambers by operating said valve body to the closing position and thereby the spring constant of the air suspension can be enlarged. Also, by operating said path of said valve body to align with the larger diameter path of the valve container can be reduced said spring constant. Further, by operating said path of said valve body to align with the smaller diameter path the valve container can be set said spring constant at an intermediate value.
In said prior art air suspension, since a plurality of air paths corresponding respectively to a plurality of paths provided in said valve container need to be formed in said elastic assembly, a plurality of penetration holes extending radially are formed in said tubular elastic member for forming the air paths. Since various forces such as shearing and compression forces acting between the car body and said piston rod act on the tubular elastic member, the number of said penetration holes is desirably as small as possible to improve the durability of said elastic member.